Heat transfer apparatus

ABSTRACT

Disclosed herein is a heat transfer device ( 2 ), the heat transfer device comprising a heat exchanger ( 10 ) driven by movement of a fluid, a heat transfer cavity ( 6 ) and a fan ( 12 ) for creating a circulating gas flow between the heat exchanger and the heat transfer cavity. The heat transfer device ( 2 ) includes: a housing having an opening ( 14 ) for allowing an object to be inserted into the heat transfer cavity ( 6 ); an outlet valve ( 52 ) for exhausting gas and/or liquid from the heat transfer cavity ( 6 ); and a controller arranged to operate the outlet valve ( 52 ). The heat transfer device ( 2 ) may, for example, take the form of a cooling device for rapidly cooling a drinking vessel such as a beer glass.

The present invention relates to heat transfer devices that may be usedto cool or heat an object to a desired temperature, and correspondingmethods of cooling or heating an object. The invention also relates tocooling apparatus and methods of drying a heat transfer device, forexample after use.

WO 2011/042698 describes a heat transfer device for hygienic cooling ofobjects such as drinking vessels. A rapid cooling effect is achievedusing turbulence to generate a frosted effect. However this method ofrapid heat transfer requires high rates of air circulation e.g. high fanspeeds. It may be inefficient to have the fan running at high speed allthe time and, in addition, there may be potential problems with frostbuild-up. It would be desirable for a rapid frosting mode to be turnedon/off as required. However the very cold temperatures in such a coolingdevice, and the internal build-up of frost, add to the complexity ofachieving reliable means of control. The present invention seeks toimprove known heat transfer devices and corresponding methods.

According to a first aspect of the present invention there is provided aheat transfer device comprising: a heat exchanger, a heat transfercavity and means for creating a circulating gas flow between the heatexchanger and the heat transfer cavity; a housing having an opening forallowing an object to be inserted into the heat transfer cavity; asensor arranged to provide a detection signal when an object is insertedinto the heat transfer cavity; and a controller for adjusting the rateof circulating gas flow in response to a detection signal from thesensor. It will be appreciated that such a device is able tointelligently control the rate of circulating gas flow by using thesensor to detect when an object is inserted into the heat transfercavity. For example, upon receiving a detection signal from the sensor,the controller may increase the rate of circulating gas flow between theheat exchanger and the heat transfer cavity so as to enter a rapid heattransfer mode. This may be particularly efficient where the heattransfer cavity is arranged to create turbulence in the circulating gasflow. As is discussed in WO 2011/042698, a highly turbulent gas flow hasbeen found to generate a high heat transfer coefficient and therebyaccelerate heat exchange with the object. Thus, in preferred embodimentsthe circulating gas flow may be constrained to pass through a gapadjacent the object that is defined by the heat transfer cavity so as topromote turbulence in the circulating gas flow. This aspect of theinvention also includes a method of cooling or heating an object,comprising: creating a circulating gas flow in a heat transfer cavitythat can receive an object; cooling or heating the circulating gas flow;sensing when an object is inserted into the heat transfer cavity; andadjusting the rate of circulating gas flow in response to said sensing.

Some of the ways in which the rate of circulating gas flow can beadjusted are discussed further below.

It is important that the sensor can reliably detect when an object isinserted into the heat transfer cavity. While a manual switch could beused to control adjustment of the rate of circulating gas flow, forexample activated by a user when/after inserting an object, thisrequires additional interaction. It is advantageous for the device toautomatically detect an object and trigger the rapid heat transfer modewithout intervention being required. In some embodiments the sensorcomprises at least one contact sensor, for example a mechanical contactsensor such as a microswitch, that may be activated directly orindirectly when an object is inserted into the heat transfer cavity. Forexample, a contact sensor may be activated directly by the passage ofthe object through the opening or by the seating of the object in theheat transfer cavity. A pressure pad could be used to detect when anobject is present in the heat transfer cavity. Or, in another example, acontact sensor may be activated indirectly by movement of another partthat takes place when an object is inserted into the heat transfercavity, e.g. movement of a seal that closes the opening when an objectis not present.

The Applicant has found that the reliability of a contact sensor can bereadily degraded by environmental factors. Especially when the heattransfer device is a cooling device, a tendency for ice to build up caninterfere with proper operation of a contact sensor. It is thereforepreferable for the sensor to comprise at least one non-contact sensor.Appropriate non-contact sensors may include sensors for electromagneticradiation (e.g. optical, near-infrared, far-infrared, ultraviolet),ultrasound transducers, and capacitive sensors. Some example ofcontactless sensor arrangements will now be discussed in more detail,however, it is envisaged that other non-contact sensor technologies mayalso be employed.

In a set of embodiments the non-contact sensor may comprise an active orpassive sensor arrangement for electromagnetic radiation or ultrasound.In a passive sensor arrangement, for example, the non-contact sensor maysimply comprise a sensor that detects ambient conditions and/or a changedue to electromagnetic radiation being emitted, scattered, lensed,obstructed, absorbed or reflected by an object that is inserted in theheat transfer cavity. A passive receiver such as a photocell orphotodiode may simply detect changes in light level when an object isinserted, e.g. increased brightness as an object opens a seal thatcloses the opening or reduced brightness when an object prevents ambientlight from reaching the sensor. In other examples the sensor maycomprise a vision camera that provides an optical image of the openingand/or heat transfer cavity and uses appropriate software to determinewhen an object is inserted or present. However such passive opticalsensors are sensitive to ambient lighting conditions, which may behighly variable e.g. at different times of day. A heat transfer deviceused to cool glasses may be located in a bar or nightclub with flashinglights.

In yet other examples, the sensor may comprise an infrared (IR) sensorthat detects changes in thermal emission when an object is inserted intothe heat transfer cavity, preferably a far-infrared (FIR) sensor. Thesensor may comprise a simple IR thermopile or an IR camera that imagesthe infrared radiation emitted by the object and its surroundings. Asthe object will likely be at a different temperature to the heattransfer cavity when it is first inserted (e.g. a warm object entering acool cavity), the infrared sensor or camera can use the change in signalor contrast in a thermal image to generate a detection signal. A passiveinfrared sensor using thermal emission can provide reliable results evenif there are changing ambient light conditions. In some embodiments theIR sensor or camera may be positioned above the opening and, optionally,angled to look down on the opening. This may ensure that the sensor hasa good view of the normally cold interior environment of the heattransfer cavity and is therefore sensitive to temperature change when anobject is inserted into the cavity. In an active sensor arrangement, thenon-contact sensor may comprise a radiation emitter and a radiationreceiver that detects reflection and/or transmission of the emittedelectromagnetic radiation. This can reduce the arrangement's sensitivityto background illumination. For example, the sensor can detect abackground radiation reading when the emitter is off and compare thisvalue to the reading when the emitter is on. In addition, oralternatively, the radiation emitter may emit frequencies of theelectromagnetic spectrum that are not visible to the human eye, e.g.near-IR or ultraviolet light, so as to avoid light beams that couldpotentially annoy or distract a user. Ultraviolet may be more readilyreflected or scattered by an object being detected, but there may berisks associated with the use of ultraviolet radiation in closeproximity to a user who is inserting the object. An infrared sensorarrangement may be preferred for user safety. In particular, a sensorarrangement comprising an infrared emitter operating in a narrow band,e.g. the wavelength range of 800-1000 nm, has the advantage of thereceiver being able to readily filter out broadband sources such asartificial lighting. Such arrangement can conveniently be achieved usinglow-cost emitters (e.g. infrared LEDs) and receivers (e.g. infraredphotodiodes) that are readily available.

In various embodiments it can be desirable for a radiation sensor (e.g.operating at visible or infrared wavelengths) to detect an object, suchas a drinking vessel, that is made of transparent material e.g. glass orclear plastic. This can make it difficult for the non-contact sensor tooperate in a transmission mode as radiation may shine straight throughthe object. One possibility is for such objects to include opaquemarkings (for example printed or etched on the transparent material)that can obstruct the transmitted radiation to increase detection.However this may not be feasible or desirable to implement in practice.

Even a reflectance sensor can be hindered by the shiny nature of suchmaterials, making it difficult to differentiate between reflection ofthe emitted radiation from the object and background reflections fromthe ambient illumination. A non-contact sensor comprising a radiationemitter and a radiation receiver, operating in a reflection mode, may beangled so as to better pick out reflections from an expected object.However the angle of such reflectance measurements may need to beadjusted for different objects and this can reduce the reliability ofthe sensor when the device is used with more than one size or type ofobject, e.g. different glass shapes.

In another example, a non-contact reflectance sensor may use binocularrange sensing to determine the distance to an object from a correlationof the radiation reflected and/or scattered by the object. Such a sensorarrangement may be able to differentiate between the weak reflectionsfrom a transparent object (such as a glass) and background lightreflections. An infrared proximity sensor such as the Sharp GP2Y0A21YKmay be suitable.

The Applicant has devised a novel kind of active sensor arrangement,comprising an electromagnetic radiation emitter and receiver, that candetect an object from transmission of the emitted radiation. Thisarrangement can be particularly suitable for transparent objects thatmay have a lensing effect on a transmitted beam. In such preferredembodiments the non-contact sensor comprises an electromagneticradiation emitter and a corresponding electromagnetic radiation receiverarranged on opposite sides of the opening to define a transmission pathpassing through an object that is inserted through the opening. In theabsence of an object the transmission path may be straight. When atransparent object, such as glass drinking vessel, is present in theopening it can have a beam bending effect so that the emitted radiationdoes not follow the transmission path to reach the receiver. This effectmay be optimised by arranging the radiation emitter and receiver at aheight (e.g. at, above or below the opening) corresponding to theexpected height of a detectable feature on an object when insertedthrough the opening, for example a height corresponding to the thickenedbase of a glass or some other feature e.g. etched onto the glass. It canbe advantageous for the sensor to be sensitive to objects of aparticular height as this can ensure that the device only operates withcertain objects, for example intended glassware.

The radiation emitter and receiver may be arranged diametrically onopposite sides of the opening, so as to define a transmission pathpassing through a region central to the opening. However, the Applicanthas surprisingly found that the beam bending effect may be greater foran off-centre transmission path. It is therefore preferable that theradiation emitter and receiver are arranged non-diametrically onopposite sides of the opening, so as to define an off-centretransmission path. This makes it more likely for an intervening objectto deflect the emitted radiation from the transmission path so that itdoes not reach the receiver. The sensor may compare an output from thereceiver with a preset threshold to determine when an object is presentin the transmission path. Preferably the emitter is a pulsed source ofradiation. This enables the sensor to compare the radiation receivedwhen the emitter is on and off. In addition, or alternatively, thesensor may filter the output from the receiver so as to be sensitive toa wavelength of the emitted radiation.

Another example of an active sensor arrangement uses ultrasound. Thenon-contact sensor may comprise an ultrasound transducer or transceivere.g. arranged to emit an ultrasound pulse and detect reflection of thepulse when an object is inserted through the opening and/or present inthe heat transfer cavity. The ultrasound transducer may be continuallypulsed and the time-of-flight measured for reflections. A longertime-of-flight for reflections crossing the opening and/or the heattransfer cavity may indicate the absence of an object while a shortertime-of-flight may indicate the presence of an object. A suitable typeof ultrasound sensor is the SRF series available from Devantech Ltd. Anadvantage of such an ultrasonic range sensor is that it may be able todetect the presence of wide range of different objects, regardless oftheir optical properties. A detection signal provided by an ultrasoundtransducer may be less sensitive to the build-up of frost on an objectbeing cooled, which could interfere with electromagnetic sensingtechniques. Such an ultrasound transduce is preferably waterproof, so asnot to be affected by condensation or ice.

In another set of embodiments the non-contact sensor may comprise acapacitive sensor arrangement. Many objects are made of insulatingmaterials, such as ceramic or glass, which have a relatively highpermittivity. For example, glass has a relative permittivity of betweenaround 4 and 10, which gives good detectability in air using capacitivesensing. The capacitive sensor arrangement may operate by excitingelectrodes to different voltages (e.g. using a high frequency signal)and monitoring current, e.g. the charge transferred for a given voltagechange or the lead time between current and voltage. In various examplesthe capacitive sensor arrangement may comprise at least one electrodearranged to sense a capacitance change indicating proximity of an objectinserted through the opening and/or into the heat transfer cavity. Sucha capacitive sensor arrangement may comprise a pair of electrodesarranged to generate a fringe field that will be interrupted when anobject is inserted into the heat transfer cavity. However, the Applicanthas found that off-the-shelf fringe field capacitive sensors may notprovide sufficient sensitivity as they typically require an object toapproach within a few millimetres for detection. This can cause aproblem if objects of different size or dimensions are inserted into theheat transfer cavity. Furthermore, in a cooling device a typicalcapacitive sensor may be sensitive to frost build-up and provide falsereadings. For example, the Applicant has found that a thin layer of icein close proximity to a capacitive sensor can give a reading that isvery similar to that of a glass-walled object such as a drinking vessel.The Applicant has devised a novel capacitive sensor arrangement that maybe particularly suitable for a heat transfer device in which the heattransfer cavity is shaped to receive a hollow object such as a drinkingvessel. The capacitive sensor arrangement preferably comprises a pair ofelectrodes arranged in the heat transfer device to receive an objecttherebetween. The electrodes may be at least partially annular andpreferably arranged concentrically so that an object, such as a drinkingvessel, can be received between inner and outer electrodes. Theelectrodes may not be fully annular, so as to save on material, but theApplicant has found that a higher surface area is beneficial to helpeliminate sensitivity to local ice build-up and improve reliability ofobject detection. The electrodes may therefore be substantiallycylindrical or frustoconical.

In a preferred set of embodiments the heat transfer cavity may beformed, at least in part, by a separable and/or removable ductingmember. For example, the ducting member may comprise a generallycylindrical sheath that is shaped to receive an inverted drinking vesselsuch as a beer glass. It is advantageous for the ducting member to be aseparable insert so that it can be removed from the device to becleaned. A further advantage is that different ducting members may befitted to match different drinking vessels in use, without needing tochange the rest of the device. This can be particularly beneficial whenthe ducting member defines a gap adjacent the object that is chosen topromote turbulence in the circulating gas flow. In embodiments where thesensor comprises a capacitive sensor arrangement, the ducting member mayconveniently position or carry one or more of the electrodes. Althoughthe ducting member may be formed of plastics material(s), it can carry aconductive e.g. metallic layer or conductive coating to form theelectrode(s). Where the electrode(s) are carried by the ducting memberthen a separable electrical connection may be provided. Otherwise theelectrode(s) may be positioned inside or outside the ducting member witha permanent electrical connection. In a further set of embodiments thecirculating gas flow may be created by a fan positioned inside or belowthe heat transfer cavity, for example beneath the ducting member. Thegas flow may be circulated by the fan through a generally cylindricalexhaust tube that is arranged concentrically inside the ducting member.The exhaust tube can conveniently position or carry one of theelectrodes of a capacitive sensor arrangement, e.g. without the need fora separable electrical connection.

Of course it will be appreciated that the heat transfer device mayinclude more than one sensor, in particular one or more of the differentsensor arrangements discussed above, in any combination. The use ofmultiple sensors may provide for increased reliability, with a detectionsignal being required from more than one sensor before the controlleroperates. In addition, or alternatively, the use of multiple sensors mayprovide a failsafe in the event that one of the sensors becomesinoperative e.g. due to frost build-up in a cooling device. In apreferred set of embodiments the sensor(s) are chosen so as to detectwhen a drinking vessel is inserted into the heat transfer cavity. Thesensor(s) may be integrated with an opening and/or heat transfer cavitythat are sized or shaped to receive a given type of drinking vessel, forexample a particular kind of beer glass. As is mentioned above, thesensor(s) may be arranged so as to provide a detection signal only whena certain type of drinking vessel is inserted, e.g. to prevent thedevice from being used with certain beer glasses.

There will now be described some further features of the heat transferdevice that apply irrespective of the type of sensor.

In some examples the device may not operate when an object is notpresent, and the rate of circulating gas flow may therefore be increasedfrom zero upon detecting that an object is inserted into the heattransfer cavity. However, in many examples it is preferable for thedevice to operate at least in a standby mode, with a certain minimumrate of circulating gas flow, so as to help maintain the heat transfercavity within a certain temperature range even when an object is notpresent. In a particularly preferred set of embodiments, the heattransfer device is a cooling device and the heat exchanger is a thermalsink arranged to cool the circulating gas flow. For example, the minimumrate of circulating gas flow may be chosen to maintain the heat transfercavity at a temperature in the range of about −35° C. to −45° C. Whenthe sensor detects that an object has been inserted into the heattransfer cavity, the controller may increase the rate of circulating gasflow so as to enter a rapid heat transfer mode, e.g. a rapid coolingmode that can create a frosted effect on the outer surfaces of theobject.

It is preferable that the rapid heat transfer mode continues only for aslong as necessary to bring the object to a desired temperature, as thehigh rate of circulating gas flow might have a high energy demand. Wherethe heat transfer device is a cooling device, it may not be desirable toprolong the rapid cooling mode as this could result in an unwantedbuild-up of ice on the object or in the heat transfer cavity. Duringrapid circulation, any ambient (typically damp) air that leaks into theheat transfer cavity will be mixed in more, and for a cooling devicethis can cause excess frost as well as requiring extra energy input. Inaddition, the means for creating the circulating gas flow (e.g. a fan)may dissipate significant energy during operation, both demanding energyand requiring further cooling of the heat transfer cavity, therebylowering the efficiency of the device. In various examples the rapidcooling mode is terminated once a desired frosting effect has beenachieved for the object. Preferably the controller reduces the rate ofcirculating gas flow after an object has undergone a desired heattransfer treatment.

In a set of embodiments the sensor may further be arranged to detectwhen an object is removed from the heat transfer cavity. The controllermay then adjust the rate of circulating gas flow in response to afurther detection signal from the sensor indicating removal of thecooled/heated object. Preferably the controller decreases the rate ofcirculating gas flow so as to enter a standby mode. As is mentionedabove, the standby mode could be one in which the circulating gas flowis turned off completely, or a “keep cold/warm” mode where the gas flowis circulated at a lower rate to maintain the heat transfer cavitywithin a particular temperature range. However there may be times whenan object is inserted into the device and not removed for immediate usebut instead left inside the heat transfer cavity. A user may forget toremove the object or may choose to leave the object in a cooled/heatedstate until it is required. It would be inefficient for the device tomaintain the rapid heat transfer mode indefinitely. The device mayprovide a user alert when the controller determines that an object isready to be removed, but it may be desirable to switch out of the rapidheat transfer mode without needing to remove the object.

In another set of embodiments, alternatively or in addition, thecontroller may be further arranged to adjust the rate of circulating gasflow so as to exit the rapid heat transfer mode, e.g. in response to amanual input, a timer signal or a temperature signal. In a first set ofexamples a user may provide a manual input when it is judged that theobject has been heated/cooled to a desired degree. This allows a user todictate the result that is achieved and makes the device more flexible.However it may instead be desirable to avoid a perception of variabilityand ensure that a repeatable heat transfer treatment is achieved by thedevice automatically ending the rapid heat transfer mode.

In a second set of examples, alternatively or in addition, thecontroller may respond to a temperature signal indicating that theobject has reached a desired temperature. The temperature signal may beprovided by the same sensor that detects when an object is inserted, ora further sensor, for example a passive infrared sensor. In a third setof examples, alternatively or in addition, the controller may respond toa timer signal. For example, the controller may set a simple time limittriggered by the detection signal when an object is first inserted intothe heat transfer cavity. The controller may be programmed withdifferent time limits for different objects, which could be set manuallyor informed by the detection signal (e.g. based on the type of objectthat is detected). In at least some examples, the controller may monitora temperature signal or a timer signal during the rapid heat transfermode and determine the length of time left in that mode. An audibleand/or visible countdown may be provided to inform a user of how longthe object needs to stay in the heat transfer device. Of course one ormore of these techniques may be provided in the same device, for examplea default timer in case a user does not remove the object from the heattransfer cavity or its removal is not detected for some reason. When thecontroller operates to adjust the rate of circulating gas flow so as toexit the rapid heat transfer mode, a communication signal may be outputby the device. The communication signal may comprise an audible and/orvisible alert to a user that the rapid heat transfer mode has ended ande.g. the object is ready to be removed. As is mentioned above, as adefault the device may operate in a standby mode with a certain minimumrate of circulating gas flow, so as to help maintain the heat transfercavity within a certain temperature range even when an object is notbeing rapidly cooled/heated. Where the device is a cooling device, ithas been found beneficial to maintain relatively cold temperaturesthroughout the internal gas flow path by recirculating the cold gas,e.g. so that temperatures remain cold even further away from the heatexchanger. In embodiments where the circulating gas flow is generated bya fan or other mechanical device, such a standby mode can prevent icebuild-up from locking the moving parts, as might occur if there was zerocirculation in between rapid cooling modes.

In a set of embodiments the device operates in a standby mode where theheat exchanger is operating (e.g. circulating refrigerant through heatexchange coils) and there is a gas flow circulating between the heatexchanger and the heat transfer cavity. The gas flow may be circulatedat a lower rate than in the rapid heat transfer mode. Preferably theheat exchanger is driven to provide substantially the same heat transferrate in the standby mode as in the rapid heat transfer mode (for a givenrate of circulating gas flow). For example, refrigerant may becirculated through the heat exchanger at the same rate and temperature.Of course the rate of circulating gas flow does not need to stayconstant in the standby mode but could be adjusted, e.g. based on atemperature measurement for the heat transfer cavity. In such a standbymode the heat transfer cavity of a cooling device may, for example, bemaintained in a range of about −35° C. to −45° C. This may be considereda “peak” standby mode as the heat transfer cavity is kept at temperaturerange quite far from ambient and is ready to move into a rapid heattransfer mode at any time. Such a “peak” standby mode would be ideal fora device that is in regular use, for example to frost glasses in a barduring evening service.

The Applicant has recognised that there may be “off-peak” times when itis desirable to keep the device running, but with a lower energy demand,e.g. when objects may still need to be cooled/heated but less frequentlythan at peak times of use. One option could be to further adjust e.g.reduce the rate of circulating gas flow. However, without a certain rateof recirculation it has been found that ambient air can more readilyleak into the heat transfer cavity and quickly change its temperature.Where the heat exchanger is passive, e.g. fins simply arranged toexchange heat with the atmosphere, there may be little scope to changeits effect on the circulating gas flow. On the other hand, it has beenrecognised that an active heat exchanger can provide for control of thecooling/heating effect without necessarily adjusting the rate ofcirculating gas flow. Thus, in preferred embodiments, the heat exchangeris driven to provide a first heat transfer rate for a given rate ofcirculating gas flow in a first (“peak”) mode of operation, and asecond, lower heat transfer rate for the same given rate of circulatinggas flow in a second (“off-peak”) mode of operation. A controller may bearranged to switch between the first and second modes of operation. Thisis considered novel and inventive in its own right. According to asecond aspect of the present invention there is provided a heat transferdevice comprising: a heat exchanger, a heat transfer cavity and meansfor creating a circulating gas flow between the heat exchanger and theheat transfer cavity, wherein, in a first (“peak”) mode of operation,the heat exchanger is driven to provide a first heat transfer rate for agiven rate of circulating gas flow and, in a second (“off-peak”) mode ofoperation, the heat exchanger is driven to provide a second, lower heattransfer rate for the same given rate of circulating gas flow; and acontroller arranged to switch between the first and second modes ofoperation. It will be appreciated that such a device can be controlledso as to switch between “peak” and “off-peak” modes of operation withoutnecessarily adjusting the rate of circulating gas flow. By activelydriving the heat exchanger to provide different average heat transferrates, the temperature of the heat transfer cavity may be allowed tochange but the circulating gas flow can ensure that there is an eventemperature distribution. This can keep the device primed so that adesired cooling/heating effect is achieved when an object is insertedinto the heat transfer cavity and the controller then adjusts the rateof circulating gas flow e.g. so as to enter a third, rapid heat transfermode. In the context of vapour-compression refrigeration, it will beunderstood that what is meant by the heat exchanger being “driven” isthe heat transfer rate achieved as a result of movement of a coolantfluid therein, for example movement of a refrigerant in the coils of aheat exchanger. This may depend on factors including (but not limitedto) the choice of fluid driving the heat exchanger, the fluid flow rate,and the temperature of the fluid before it undergoes heat exchange. Inthe context of thermoelectric heat transfer using the Peltier effect,the heat exchanger may be “driven” at different heat transfer rates byvarying the voltage applied across (or current through) the solid statedevice. Other types of heat exchanger may also be envisaged that allowfor the heat transfer rate to be adjusted e.g. depending on the powersupplied to the heat exchanger.

This aspect of the invention also includes a method of cooling orheating an object, comprising: creating a circulating gas flow in a heattransfer cavity that can receive an object; cooling or heating thecirculating gas flow; in a first (“peak”) mode of operation, cooling orheating the circulating gas flow at a first heat transfer rate for agiven rate of circulating gas flow; in a second (“off-peak”) mode ofoperation, cooling or heating the circulating gas flow at a second,lower heat transfer rate for the same given rate of circulating gasflow; and switching between the first and second modes of operation.

In preferred embodiments, the controller is arranged to switch to athird mode of operation wherein the given rate of circulating gas flowis adjusted when an object is inserted into the heat transfer cavity.For example, the given rate of circulating gas flow may be increased toprovide a rapid heat transfer mode. In the third mode of operation theheat exchanger may also be driven to provide the first, higher, heattransfer rate. Where the device is starting in the second (“off-peak”)mode, the heat exchanger may therefore be adjusted at substantially thesame time as adjusting the rate of circulating gas flow. Such a rapidheat transfer mode may be triggered manually or automatically. Inexamples of the latter, the heat transfer device may comprise a sensorarranged to detect when an object is inserted into the heat transfercavity. Any of the sensor features described hereinabove may equallyapply to such embodiments.

It will be appreciated that the starting temperature of the heattransfer cavity in the third mode of operation may be different,depending on whether the controller has switched from the first (“peak”)mode or the second (“off-peak”) mode to the third mode. Where the heattransfer device is a cooling device, for example, the heat transfercavity may be warmer starting from the second (“off-peak”) mode. It maytherefore take longer to achieve a desired cooling effect, for exampleto frost a drinking vessel. The time spent in the third mode ofoperation, for example to achieve rapid cooling of an object insertedinto the heat transfer cavity, can be adjusted to take this intoaccount. Thus in a preferred set of embodiments the controller isarranged to switch to the third mode of operation for a time period thatis adjusted, preferably lengthened, depending on the preceding mode ofoperation, e.g. peak or off-peak. During a generally off-peak period ofusage, an increased frosting time may be acceptable and canadvantageously compensate for the warmer starting temperature of theheat transfer cavity. Accordingly the controller is preferably arrangedto switch to the third mode of operation for a time period that islonger when the preceding mode of operation is off-peak rather thanpeak. This may also be more energy efficient, as it has been found thatwhen the device is used less frequently the heat transfer cavity onlywarms due to heat gain through its insulation as there is little mixingwith ambient air from objects being inserted. However, if the controllerwere to detect an increase in usage indicating that the off-peak mode isno longer appropriate, then it may act to re-adjust the time period forrapid heat transfer despite the preceding off-peak mode. For example,the controller may react to increased load (e.g. multiple glassfrostings requiring a higher throughput) in the third mode of operationto provide a faster cooling period than the lengthened one, despite thepreceding off-peak mode, thereby maximising performance and efficiency.

As is mentioned above, the controller may switch from either the first(“peak”) mode or the second (“off-peak”) mode to the third mode ofoperation, e.g. in response to a detection signal that an object hasbeen inserted into the heat transfer cavity. If the device has beenoperating in the off-peak mode for some time then it may be desirable tocontrol the heat exchanger so as to move back to the first, higher, heattransfer rate in the third mode. However, if the device has onlyrecently switched to the off-peak mode then there may have been littleor no change in the temperature of the heat transfer cavity and noinstant need to increase the heat transfer rate. The device may beswitched back to the off-peak mode after the third mode has provided forrapid cooling/heating of the object. So as to avoid cycling the heatexchanger unnecessarily, the controller may use a timer to determinewhether to change the heat transfer rate at the same time as adjustingthe rate of circulating gas flow when entering the third mode. Forexample, the controller may only switch the heat exchanger to the first,higher, heat transfer rate in the third mode when the timer determinesthat the device was operating in the second (“off-peak”) mode for aminimum preceding delay, e.g. at least two minutes.

Where the heat transfer rate of the heat exchanger is also dependent onthe temperature of the heat transfer cavity, this is assumed to beconstant for the purpose of comparing the (average) first and secondheat transfer rates. It will be appreciated that the heat transfer rateof the heat exchanger may be actively adjusted in any suitable way. Invarious embodiments the heat exchanger may form part of a heat exchangecircuit driven by movement of a fluid therein to provide the first orsecond heat transfer rate. For example, the heat transfer rate may beadjusted by controlling the temperature and/or speed of the fluid. Wherethe heat transfer device is a cooling device, for example, the heatexchanger may form part of a refrigerant circuit driven by a movingcoolant fluid e.g. a refrigerant. In the second (“off-peak”) mode ofoperation the heat transfer rate may be lowered by reducing or stoppingmovement of the coolant fluid through the heat exchanger, or by reducingthe degree of cooling of the coolant fluid before it reaches the heatexchanger. For instance, in a typical refrigerant circuit the coolantfluid is circulated through a compressor (and optionally a condenser)e.g. a condensing unit before being passed to the heat exchanger andthis may be controlled. A variable speed compressor may be used. Theheat exchange circuit may be controlled in response to a temperaturesignal from a sensor located in the heat transfer cavity.

In the second (“off-peak”) mode of operation the entire heat exchangercould be pulsed on and off to provide a second heat transfer rate thatis, on average, lower than the first heat transfer rate. Even when theheat exchanger is not being actively driven, its thermal mass (forexample, the copper coils that carry the coolant fluid) can continue toprovide a cooling effect e.g. even when the condensing unit (inparticular the compressor) is turned off. This may continue to cool (orheat) the circulating gas flow in the heat transfer cavity. Howeverconstant cycling of all the components in a heat exchange circuit, suchas a refrigerant circuit, may cause excessive wear or other damage. Insome embodiments the heat exchanger may be driven to provide a lowerheat transfer rate that is not zero i.e. the heat exchanger keepsrunning but with a lower heat transfer effect. As is mentioned above, inembodiments where the heat transfer device is a cooling device and theheat exchanger is driven by movement of a coolant fluid provided by arefrigerant device, a lower heat transfer rate may be achieved bycirculating the coolant fluid at a reduced rate. This may be beneficialin that it keeps the refrigerant device loaded. In other embodiments theheat exchanger may be turned on and off, but using a timer control toensure that such cyclic operation is not too frequent, e.g. a minimumtime delay of two minutes between switching of the first and secondmodes.

Where the heat transfer device is a cooling device, in the second(“off-peak”) mode of operation the heat transfer cavity may bemaintained at a higher temperature than in the first (“peak”) mode ofoperation e.g. an off-peak temperature range of about −25° C. to −35° C.compared to a peak temperature range of about −35° C. to −45° C.

In some embodiments the controller may be arranged to switch between thefirst and second modes of operation in response to a manual input. Forexample, a user may decide when an off-peak mode is appropriate.Alternatively, or in addition, in some embodiments the controller may bearranged to automatically switch between the first and second modes ofoperation. For example, the controller may be programmed tointelligently switch between peak and off-peak modes e.g. based onhistorical or learned usage information. Usage information might includethe frequency of use (e.g. how often an object is inserted to becooled/heated), the time of day, different days of the week, the time ofyear, and even environmental factors such as the ambient temperature.

In a set of embodiments the controller may switch between the first andsecond modes of operation in response to a temperature signal from asensor located in the heat transfer cavity. For example, a coolingdevice may be switched (back) into the peak mode when warming of thecavity indicates a higher frequency of use. Alternatively, or inaddition, in a set of embodiments the controller may switch between thefirst and second modes of operation in response to a detection signalfrom a sensor arranged to detect when, and how frequently, an object isinserted into the heat transfer cavity. This may provide for a fasterreaction to increased usage than waiting for a temperature indication.As is mentioned above, repeated switching of the heat exchanger may bedetrimental and the controller may therefore include a timer todetermine when the heat transfer rate was last changed. For example, thecontroller may only switch back and forth between the first and secondmodes of operation after a predetermined delay, e.g. at least twominutes.

While the heat transfer device may be operated in various differentmodes as described above, from time to time the device may be switchedoff completely and the heat transfer cavity allowed to return to ambienttemperature. Especially in embodiments were the heat transfer device isa cooling device, the low internal temperatures of the heat transfercavity can cause frost i.e. ice crystals to build up. When an object isinserted through the opening, ambient air may be drawn into the heattransfer cavity and, as it cools below its dew point, any water vapourcarried by the ambient air will condense and freeze. Much of theresulting frost may be deposited on the outer surfaces of the object,contributing to a frosted effect, but after prolonged periods of usesome frost may also start to build up in the heat transfer cavity andpath of the circulating gas flow. This can have a detrimental effect oncomponents such as the heat exchanger and a fan (or other means) thatcreate the circulating gas flow. The device may therefore be turned offfrom time to time so that it can be defrosted.

When a cooling device is turned off and allowed to warm up, any residualice will melt and water is likely to collect in the heat transfercavity. Similarly, if a warming/heating device is turned off and allowedto cool down, condensation is likely to form in the heat transfercavity. The melt water or condensate could be left to evaporatenaturally, but this may take some time, especially in more humidclimates. The Applicant has recognised that it may cause potentialhygiene issues for water to be left stagnating in the device, especiallyif objects such as drinking vessels are to come into contact with theheat transfer cavity when the device is next used. It is thereforepreferable that the device can be operated in a further “defrost” or“warm-up” mode that helps the heat transfer cavity to dry out when thedevice is no longer in use. Preferably the device includes an outletvalve for exhausting gas and/or liquid from the heat transfer cavity. Acontroller may be arranged to operate the outlet valve.

According to a third aspect of the present invention there is provided aheat transfer device comprising: a heat exchanger driven by movement ofa fluid therein, a heat transfer cavity and a fan for creating acirculating gas flow between the heat exchanger and the heat transfercavity;

a housing having an opening for allowing an object to be inserted intothe heat transfer cavity;an outlet valve for exhausting gas and/or liquid from the heat transfercavity; and a controller arranged to operate the fan and/or outletvalve.

Such a heat transfer device is therefore provided both with a mainopening for the heat transfer cavity and an additional outlet valve thatcan be used to drain liquid from the cavity e.g. when it is defrosting.It will be appreciated that an outlet valve, rather than merely anoutlet or exit opening, can be opened and closed so as to selectivelyexhaust fluid from the heat transfer cavity.

This aspect of the invention includes a method of drying a heat transferdevice comprising a heat transfer cavity that can receive an object, themethod comprising: creating a circulating gas flow in the heat transfercavity; ceasing to cool or heat the circulating gas flow; and opening anoutlet valve to exhaust gas and/or liquid from the heat transfer cavity.The method optionally further comprises: increasing the rate of thecirculating gas flow.

In a drying or “defrost” mode of operation the heat exchanger is nolonger driven and the controller may open the outlet valve. In addition,the controller may optionally operate the fan so as to create ormaintain the circulating gas flow. In preferred embodiments thecontroller may operate the fan at an increased speed so as to circulatethe gas flow more rapidly. The fan may, for example, be operated tocreate an increased rate of circulating gas flow e.g. corresponding to arapid cooling mode as described above. The circulating gas flow has beenfound to help exchange heat and moisture with the external environmentthrough the outlet valve. An increased rate of circulating gas flow canquickly act to clear droplets of water resulting from condensationand/or melted frost. Furthermore, the increased workload on the fan willtend to result in heat dissipation into the heat transfer cavity thatcan also contribute to the efficiency of the defrost mode, helping todry out the heat transfer cavity. The fan is preferably in fluidcommunication with the heat transfer cavity. Further preferably the fanis waterproof e.g. comprising potted or coated electronic components soas to be unaffected by moisture ingest.

The Applicant has recognised that the design and position of the outletvalve can be optimised so as to increase the efficiency of the drying ordefrost mode.

In a preferred set of embodiments the outlet valve comprises an outletopening and the heat transfer cavity comprises an outlet flow patharranged to direct liquid towards the outlet opening. This can assist indraining larger liquid droplets under gravity. The outlet flow path maybe inclined (e.g. angled or curved) in one or more directions to ensurethat liquid is drained from throughout the cavity. For example, theoutlet flow path may be inclined downwardly in a radial direction so asto direct liquid towards the outlet opening. For example, alternativelyor additionally, the outlet flow path may be inclined downwardly in acircumferential direction so as to direct liquid towards the outletopening. In a preferred set of examples, the outlet flow path mayprovide a helical incline towards the outlet opening. In other words,the surface(s) in the heat transfer cavity may be inclined so as toprovide a spiral flow path that directs liquid towards the outletopening. This is considered novel and inventive in its own right.

According to a fourth aspect of the present invention there is provideda heat transfer device comprising: a heat exchanger, a heat transfercavity and means for creating a circulating gas flow between the heatexchanger and the heat transfer cavity; a housing having an opening forallowing an object to be inserted into the heat transfer cavity; and anoutlet valve for exhausting gas and/or liquid from the heat transfercavity; wherein the heat transfer cavity comprises an outlet flow patharranged to direct liquid towards the outlet valve.

As is described above, the outlet flow path may be inclined downwardlyin a radial and/or circumferential direction so as to direct liquidtowards the outlet valve under gravity. The outlet flow path may providea helical incline towards the outlet valve e.g. a spiral flow path thatdirects liquid towards the outlet valve.

In addition, or alternatively, in a preferred set of embodiments theoutlet valve comprises an outlet opening that is directed substantiallytangential to the direction of the circulating gas flow e.g. the outletopening is directed in the direction of rotation of the fan. This makesit easier for the outlet opening to entrain water droplets that arecarried by the circulating gas flow. Any spray that is flung outtangentially by the fan can be collected effectively to drain throughthe outlet opening. The outlet opening may be substantially positionedat a periphery of the fan. The outlet opening is therefore positioned ata point of high gas pressure relative to the opening of the heattransfer cavity, such that, with the outlet valve open and without aperfect seal at the opening of the heat transfer cavity, the twointernal pressures equilibrate each side of the ambient externalpressure. In other words, the opening to the heat transfer cavity is ata low pressure part of the air circulation path while the outlet openingis at a high pressure part. As such, the pressure of the gas just insideof the opening of the heat transfer cavity is lower than the ambientpressure so gas is readily drawn into the heat transfer cavity, and thepressure of the gas just inside the outlet opening is higher than theambient external pressure, causing gas to be readily expelled. A goodthroughflow of air is therefore created to assist in driving outmoisture and drying out the cavity. Smaller liquid droplets will readilyevaporate in the circulating gas flow, especially as it is replenishedby drier ambient air.

The Applicant has found that the outlet opening, and optionally theoutlet flow path, should be unrestrictive to the throughflow of air. Ifthey are sized too small then boundary effects can hinder the flow.Preferably the outlet opening has a cross-sectional area of at leastabout 50 mm². Where provided, the outlet flow path preferably has across-sectional area of at least about 50 mm² along its length. Thecross-sectional area of either, or both, of these is further preferablyat least about 100 mm², 150 mm², 200 mm², 250 mm², or 300 mm². In apreferred set of embodiments the outlet opening has a cross-sectionalarea of at least 250 mm², and preferably more than 300 mm², so as to dryout a typical heat transfer cavity for a beer glass in a relativelyshort period of time e.g. about 20 minutes (depending on ambientconditions). It will be appreciated that such an outlet opening islarger than a standard liquid outlet e.g. provided for drainage purposeswithout enabling an air flow. In at least some embodiments, the outletopening may have a maximum cross-sectional area of about 0.25 m². Thisensures that the heat transfer cavity is not overly open to the externalenvironment.

While it is beneficial that the outlet opening does not unduly restrictair flow, it has been found that liquid droplets can tend to form arounda larger opening and be blown out in all directions. It is desirable tobe able to collect any liquid droplets that drain through the outletopening. Thus in a set of embodiments the device further comprises afunnel arranged adjacent to the outlet valve to collect liquid. Theoutlet opening may extend orthogonally to the funnel, for example, agenerally horizontal outlet opening that directs liquid droplets into agenerally vertical funnel. The outlet opening of the valve may include aprotrusion, e.g. an angled protrusion, that tends to collect liquid intocoalesced droplets. Such a protrusion may be positioned above the funnelso that liquid droplets are directed into the funnel. The funnel mayhave a smaller cross-sectional area than the outlet opening, especiallyif the cross-sectional area of the funnel decreases to a minimum alongits length. However, it has been found that the proximity of the funnelto the outlet opening means that it can also act to restrict air flowthrough the outlet valve if the funnel is too narrow. Preferably thefunnel has a minimum cross-sectional area of at least about 30 mm², andpreferably at least about 50 mm², so that it does not negatively affectthe time taken to defrost the device. The device may further comprise adrip tray positioned beneath the funnel, preferably a removable driptray. Melt water collected in the drip tray can be left to evaporate orthe drip tray may be emptied by a user.

The controller may open the outlet valve in the drying or “defrost” modeof operation by any suitable means. So as to ensure that the valve opensreliably regardless of the air pressure in the heat transfer cavity, theoutlet valve may be mechanically opened. For example, the controller mayoperate a servo motor or electromechanical actuator (e.g. solenoid) thatmoves a cover from the outlet opening. The cover may be a sealing cover,for example an elastomeric e.g. silicone flap. The controller mayfurther operate to close the outlet valve at the end of the defrostmode. This can help to maintain hygiene by ensuring that the heattransfer cavity is not left open to the atmosphere after it has beendefrosted. In some examples the end of the defrost mode may be triggeredby a timer. Alternatively, or in addition, in some examples the end ofthe defrost mode may be triggered by a detection signal from a sensor inthe heat transfer cavity e.g. a temperature and/or humidity sensor.

In various embodiments the heat transfer device is a cooling device andthe heat exchanger is a thermal sink arranged to cool the circulatinggas flow. The heat exchanger may be driven by movement of a coolant orrefrigerant fluid therein.

There may be times when it is desirable to accelerate the drying ordefrost mode. For example, when operating a cooling device in a humidclimate there may be times during the day when frost has built up and aquick defrost would be beneficial to prevent the ice from interferingwith performance. In a set of embodiments the device may furthercomprise a heater for the heat transfer cavity. The heater may beoperated in the defrost mode so that any frost is melted more quickly.The heat exchanger may itself act as a heater, for example by drivingthe heat exchanger with a heated fluid rather than a coolant fluid. Thismay be done in a standard refrigeration circuit by bypassing hotrefrigerant from the compressor past the condenser. In many parts of theworld, mains power is not available or is subject to unexpected powercuts. If the power supply to a cooling device is suddenly interruptedthen the heat transfer cavity will be left to warm up (or cool down) andan unhygienic pool of water is likely to collect inside. While a usermay be alerted to manually open the outlet valve in such situations,this may not be acted upon. The Applicant has recognised that the outletvalve may instead be arranged to automatically drain liquid from theheat transfer cavity e.g. upon loss of electrical power to the heatexchanger. This is considered novel and inventive in its own right.

According to a fifth aspect of the present invention there is provided aheat transfer device comprising an electrically-powered heat exchangecircuit, comprising a heat exchanger, a heat transfer cavity and a fanfor creating a circulating gas flow between the heat exchanger and theheat transfer cavity, wherein the heat transfer cavity includes anoutlet valve for exhausting gas and/or liquid, and wherein the outletvalve is automatically opened upon loss of electrical power to the heatexchange circuit.

Thus in the event that the heat exchanger and/or fan can no longeroperate due to a loss of electrical power, the outlet valve isautomatically opened so that liquid can drain from the heat transfercavity as it warms up (or cools down). This means that user interventionis not required to ensure that the heat transfer cavity is kept dry andhygienic while the device is out of use. This aspect of the inventionincludes a method of drying a heat transfer device comprising a heattransfer cavity that can receive an object, the method comprising:creating a circulating gas flow in a heat transfer cavity that canreceive an object; cooling or heating the circulating gas flow using anelectrically-powered heat exchange circuit; opening an outlet valve toexhaust gas and/or liquid from the heat transfer cavity upon loss ofelectrical power to the heat exchange circuit. The method optionallyfurther comprises: sensing loss of electrical power to the heat exchangecircuit and actively opening the outlet valve.

In a set of embodiments the outlet valve may be biased open but heldclosed by an electromechanical actuator, for example an electromagnet orsolenoid actuator. The electromechanical actuator may be connected tothe heat exchange circuit so that, when electrical power is supplied tothe circuit, the outlet valve is held closed. Upon loss of power thecircuit is broken and the electromechanical actuator automaticallyreleased so that the valve is biased open. For example, the outlet valvemay comprise an outlet opening and a spring-biased cover.

In another set of embodiments the outlet valve may be actively openedupon loss of electrical power. The device may include means formonitoring the power supply to the heat exchange circuit so as to detectwhen a power cut is happening, e.g. by detecting a drop in the powersupply voltage. The device may comprise a controller that operates toopen the outlet valve in response to a power cut detection signal.However, active opening of the outlet valve is likely to requireelectrical power, e.g. to drive an electromechanical actuator to uncoverthe outlet opening of the valve. In some examples the device may furthercomprise means for storing electrical power, such as a capacitorconnected to the outlet valve. In some examples the device may furthercomprise means for generating electrical power, such as an electricbrake arranged to convert the kinetic energy of a fan as it slows downupon power failure. In these embodiments the device can providesufficient power to open the outlet valve when a power cut occurs.

In various embodiments of a heat transfer device as described above, thecirculating gas flow between the heat exchanger and the heat transfercavity is created by a fan, preferably an electric fan. The Applicanthas found that the performance of an electric fan can be affected byelectrostatic charge separation resulting from the phase changesoccurring inside the heat transfer cavity. Especially where the heattransfer device is a cooling device, ice crystals that form in thecavity can be ingested by the fan. It is believed that electrostaticcharge separation may be caused by dry ice crystals having piezoelectricproperties. The circulating gas flow means that ice crystals can impactthe fan at high velocity (e.g. 30-50 mph) and cause a build-up of chargethat may result in arcing to the electrical components of the fan, forexample causing a malfunction of the electric motor and/or controlelectronics. In order to mitigate this risk, charge build-up may beavoided by providing the fan with rotating components that areelectrically insulated, e.g. formed of plastics material or metalliccomponents having an insulating surface coating. A preferred solution isfor the rotating components of the electric fan to be grounded. This isconsidered novel and inventive in its own right.

According to a sixth aspect of the present invention there is provided aheat transfer device comprising: a heat exchanger, a heat transfercavity and an electric fan for creating a circulating gas flow betweenthe heat exchanger and the heat transfer cavity; the electric fancomprising a rotating arrangement of vanes or blades mounted on a hub,and an electric motor driving the hub, wherein the rotating arrangementhas an electrical connection to ground.

It will be appreciated that providing the rotating arrangement itselfwith an electrical connection to ground, in addition to any earthing ofthe drive motor, can ensure that static charge is not allowed to buildup on the vanes/blades or hub. This can be particularly beneficial inexamples where the rotating arrangement is mainly formed of metalliccomponents, as is common. Such a rotating arrangement may be referred toas an impeller or rotor.

Preferably the heat transfer device is a cooling device. The earthing ofthe electric fan has been found effective in preventing charge build-upcaused by ice crystals impacting on the rotating arrangement. In one setof examples the hub is mounted to the motor by bearings that establishthe electrical connection to ground. Alternatively, a separateelectrical connection may be provided. In various embodiments it ispreferable for the electrical connection to ground to include animpedance, for example a resistor. This has been found to prevent orreduce EMC emission issues, if electrical noise is present, by reducingthe ability of the fan (especially the motor hub) to act as an antenna.

Embodiments of this aspect of the invention may include any of theaforementioned features. For example, the device may comprise acontroller arranged to operate the electric fan. The controller mayadjust the rate of circulating gas flow created by the fan in responseto one or more signals, e.g. a detection signal from a sensor when anobject is inserted into the heat transfer cavity (rapid cooling/heatingmode), or a defrost signal when the heat exchanger is turned off(defrost mode).

There will now be described some further features of a heat transferdevice or cooling device in accordance with embodiments of any aspect ofthe invention.

While the device may be filled with a particular heat transfer gas,where the housing has an opening to allow an object to be inserted intothe heat transfer cavity there is likely to be ingress of ambient air.Thus in preferred embodiments the circulating gas flow may be acirculating air flow. So as to help maintain the heat transfer cavity ina desired temperature range, and to avoid changes in moisture content,the opening is preferably arranged to minimise the entry of ambient air.It is preferable that there is only one opening into the heat transfercavity while the heat exchanger is running. In addition, the opening maybe partially or fully closed by a flexible membrane that is only pushedaside when an object is inserted through the opening. Keeping theopening closed when not in use helps pressures to equilibrate andprevents ambient air from being drawn into the cavity. In a set ofembodiments the flexible membrane comprises a plurality of flapsextending inwardly from the housing and being deformable so as to definean aperture through the opening. For example, the flaps may be formed ofa flexible polymeric or elastomeric material such as silicone. For acircular opening the flaps may extend radially inwardly. An advantage ofsuch flap arrangements is that air may be encouraged to flow downwardsthrough the aperture and down the sides of the object being inserted, sothat any moisture carried by the air is deposited on surfaces of theobject to create a frosted effect. Preferably the outer surface of theflaps provides a low coefficient of friction, especially in contact withglass, so that an object can be pushed through the aperture withoutgripping. For example, the flaps may be given a low friction coatinge.g. of PTFE, or other low friction surface finish.

In the foregoing description it will be appreciated that what is meantby a circulating gas flow is a mass of gas that is entrained to flowcontinuously in a loop between the heat exchanger and the heat transfercavity. During use of the device, and especially when an object ispresent in the cavity, the circulating gas flow may comprise asubstantially constant mass of gas e.g. air trapped inside the heattransfer cavity. Of course, the volume of any mass of gas depends on itstemperature. As mentioned above, air may enter and/or exit through theopening when an object is inserted therethrough, but preferably theopening is substantially closed at other times. The housing may also bedesigned to assist in keeping the heat transfer cavity cold and dry. Ina set of embodiments the housing comprises a flange extending upwardlyaround the opening. This flange can trap a volume of drier air, which isdenser than ambient air, directly above the opening. The height of sucha flange is preferably at least 45 mm.

A heat transfer device according to any of the aspects or embodiments ofthe invention described above may comprise a heat exchanger comprising aPeltier element, for example providing a heating or cooling effectdependent on electrical current.

Additionally or alternatively, the heat transfer device may comprise aheat exchanger driven by movement of a coolant fluid therein, i.e. theheat transfer device may be a cooling device. The coolant fluid may beprovided by an on-board refrigerant circuit. In addition, the heatexchanger may be part of an electrically-powered heat exchange circuit,and electrical power may be provided as part of the device. In otherwords, the cooling device may be a standalone unit. However, in variousembodiments it is preferable for the cooling device to be compact sothat it can easily be mounted on a bar, table or counter for use. Insuch embodiments there may be provided a two-part unit comprising thecooling device connected to a separate refrigerant device. Therefrigerant device may provide the coolant fluid and/or electricalpower. For example, the refrigerant device may comprise one or more of:an electrical power supply; a refrigerant circuit; and a controller forthe refrigerant circuit. The refrigerant circuit may include a condenserand a pump for the coolant fluid.

A typical refrigerant circuit may comprise a compressor to pressurisethe coolant fluid returning from the cooling device, a condenser toremove heat from the fluid, and an expansion device to rapidly cool thefluid before it is supplied to the cooling device. The expansion devicemay comprise a thermostatic expansion valve or a capillary tube. Whenthe expansion device is located in the refrigerant device, cold fluidtravels to the cooling device and warm fluid returns to the refrigerantdevice. It is not ideal for such two-way fluid communication to becarried by the same fluid line as the returning warm fluid then tends toraise the temperature of the cold fluid before it reaches the coolingdevice and/or because relatively thick insulation may be required. TheApplicant has recognised that cooling efficiency can be improved byseparating the expansion device from the rest of the refrigerant circuitand locating the expansion device in the cooling device instead of therefrigerant device. This is considered novel and inventive in its ownright.

Thus according to a further aspect of the present invention there isprovided a two-part cooling apparatus comprising a cooling deviceconnected to a separate refrigerant device, wherein the refrigerantdevice includes a compressor and a condenser for coolant fluid suppliedto/from the cooling device, and wherein the cooling device includes anexpansion valve. This means that the coolant fluid is still warm when itis transferred from the refrigerant device to the cooling device. Theconnection preferably provides for two-way transfer of coolant fluidbetween the refrigerant device and the cooling device. The coolant fluidtravelling to the cooling device can advantageously transfer some of itsheat to the returning fluid as they pass through the shared connection.This can improve the efficiency of the overall refrigerant circuit bylowering the temperature of the coolant fluid before it reaches theexpansion valve. Furthermore, pre-heating the coolant fluid before itreaches the refrigerant device can ensure that liquid is not returned tothe compressor, e.g. due to very cold temperatures in the cooling devicedue to non-use, protecting the compressor from damage. For example, thecooling device may be connected to the separate refrigerant device by anumbilical cord or flexible line that carries the coolant fluid. A higheraverage temperature in the umbilical cord can reduce its insulationrequirements, especially when the apparatus is in a relatively warmambient environment. As is discussed above, the refrigerant circuit maybe controlled to adjust the speed and/or temperature of the coolantfluid that is provided to the cooling device e.g. to drive the heatexchanger at a different heat transfer rate and switch betweenpeak/off-peak modes of operation. It is therefore preferable that thecontroller for the refrigerant circuit is in communication with anycontroller in the cooling device. Detection signals from sensors in thecooling device, for example an object detection sensor and/ortemperature sensor, can then be passed from the controller for thecooling device to the controller for the refrigerant circuit asnecessary. Such communication of control signals may be combined withelectrical power being supplied from the refrigerant device to thecooling device. A two-way electrical cable may be connected between therefrigerant device and the cooling device. The electrical connection(s)between the refrigerant device and the cooling device may be separatefrom refrigerant lines supplying the coolant fluid to/from the twodevices. However, in a preferred set of embodiments the two-part unitcomprises a cooling device connected to a separate refrigerant device byan umbilical cord or flexible line that also provides an electricalconnection e.g. both electrical connection and transfer of a coolantfluid.

The umbilical cord provides a tidy way to connect the cooling device toa separate refrigerant device. The two devices may be permanentlyconnected by the umbilical cord. However, in at least some embodiment,the umbilical cord includes a separable connection. This means that thecooling device can be installed separately from the refrigerant device,and different devices may be connected together. For example, in a barenvironment, a refrigerant device may be installed more permanently outof view of customers while one or more bar-top cooling device may betemporarily installed and connected to the refrigerant device whenrequired. The separable connection may include a seal for the coolantfluid, to allow for separation without leakage. So-called “quickdisconnect” couplings may be used. In at least some embodiments, theseparable connection may be poka-yoke i.e. designed so that it can onlybe connected the right way round.

To improve flexibility in the positioning of the cooling device relativeto the refrigerant device, and in routing of the umbilical, theumbilical cord is preferably connected to the refrigerant device at anangle of around 45°. This means that it can readily be bent to extendeither horizontally or vertically towards the cooling device. In variousexamples, the umbilical cord may be at least 50 cm, 60 cm, 70 cm, 80 cm,90 cm or 1 m long. Preferably the umbilical cord is at least 2 m, 3 m, 4m, or 5 m long. The umbilical cord may be up to about 10 m long.

Some embodiments of the present invention will now be described, by wayof example only, and with reference to the accompanying figures, inwhich:

FIG. 1a is a cross-sectional view of a cooling device and FIG. 1b is aschematic illustration of the circulating airflow in such a device;

FIG. 2a is a top view of a sensor arrangement across the opening of sucha cooling device and

FIG. 2b is a side cross-sectional view of the opening;

FIG. 3a and FIG. 3b show an infrared sensor arrangement to detect when aglass is inserted through the opening;

FIG. 4 shows a black and white image of passive thermal emission in thefar infrared spectrum for a glass inserted through the opening;

FIG. 5a and FIG. 5b provide a side sectional view and a perspectivesectional view of a capacitive sensor arrangement;

FIG. 6 is a side sectional view of a cooling device including anelectrical connection to earth;

FIG. 7 is a schematic side sectional view of a cooling device includingan outlet valve;

FIG. 8 is a top view of an outlet flow path in the base of the heattransfer cavity of a cooling device;

FIGS. 9a-9c provide perspective and side sectional views of the outletvalve in the base of a heat transfer cavity;

FIG. 10 is a side sectional view of a counter-top cooling device;

FIGS. 11a and 11b provide schematic side views of a counter-top coolingdevice connected to a refrigerant device by an umbilical cord; and

FIG. 12 provides a schematic overview of the components in a coolingdevice connected to a separate refrigerant device.

There is seen in FIG. 1a an exemplary cooling device 2 that may be usedto chill and frost a beer glass 4 inserted into a heat transfer cavity 6of the device 2. The heat transfer cavity 6 is defined by adouble-walled, cylindrical ducting member 8 that is shaped to receive aninverted beer glass 4. The ducting member 8 may be removable andoptionally interchangeable, for example to allow for different sizes andshapes of beer glass 4 to be positioned in the heat transfer cavity 6.Surrounding the ducting member 8 is a heat exchanger 10 in the form of aset of coils. In this example, the heat exchanger 10 is a heat sinkcomprising multiple copper coils that are cooled by a refrigerant fluidpumped there through. A fan 12 is positioned below the ducting member 8and heat exchanger 10 so as to create a circulating airflow in the heattransfer cavity 6. The schematic inset of FIG. 1b illustrates how air,or any other gas inside heat transfer cavity 6, is circulated by the fan12. As is described in WO 2011/042698, the ducting member 8 is shaped asa pseudo-negative of the glass 4 to be cooled such that there is aspecified gap between the ducting 8 and the glass 4 that promotesturbulence in the airflow. When the fan 12 is operated at high speed,the circulating airflow is highly turbulent and this generates a highheat transfer coefficient so as to achieve rapid cooling. As seen inFIG. 1b , the airflow is drawn out of the heat transfer cavity 6 by thefan 12 at (1), driven across the coils of the heat exchanger 10 at (2)and circulated around the ducting member 8 at (3), with a restrictedregion between the glass 4 and the ducting member 8 acting to acceleratethe airflow and create turbulence for optimal heat transfer with theglass at (4).

The cooling device 2 includes an outer housing defining an opening 14that allows the glass 4 or other object to be inserted into the heattransfer cavity 6. The opening 14 may be closed by a flexible membrane16 or other seal so as to help retain the cold air inside the heattransfer cavity 6. The housing provides a flange 17 extendingcircumferentially around the opening 14 and extending for a height abovethe opening. It has been found beneficial to make the flange at least 45mm high. This helps to trap a static volume of air above the opening 14,which may be cooler than ambient and hence denser. The flange 17surrounds the protruding base of a glass 4 while it is being frosted.

Various embodiments of such a cooling device will now be described withreference to the subsequent figures. Although the object inserted intothe heat transfer cavity is described as a glass, it will be appreciatedthat other objects may of course be cooled instead. Furthermore, theheat exchanger may take the form of a thermal sink or thermal sourceand, in the latter case, the heat transfer cavity may be arranged towarm rather than cool an object inserted therein.

There is seen in FIGS. 2-5 some non-contact sensor arrangements fordetecting when a glass is inserted into the heat transfer cavity of acooling device. In the example of FIGS. 2a and 2b , an active radiationsensor arrangement is used to detect when a glass 4 is inserted throughan opening 14 in the upper part of the heat transfer cavity 6. It may beseen with reference to FIG. 1a that the opening 14 is generally closedby a flexible membrane 16 that can be deformed so as to allow a glass 4to be pushed through the opening 14 and down into the heat transfercavity 6. The top view of FIG. 2a shows a flexible membrane 16 that issplit into radial flaps providing a flexible seal around the glass 4.The flaps bend against the glass 4 when it is inserted, to provide anintimate seal and encouraging any air that is pulled into the heattransfer cavity 6 to curve down the sides of the glass 4. Oncepositioned in the heat transfer cavity 6, an upper end of the glass 4protrudes above the opening 14 so as to enable the user to grip theglass when it is ready to be removed. The protruding base of the glass 4is detected by a light gate arrangement indicated generally by 18 inFIGS. 2a and 2b . The light gate 18 is defined between an infrared lightemitting diode (LED) 20 and a photodiode 22 arranged non-diametricallyopposite the LED 20. The LED emitter 20 and photodiode receiver 22 maybe filtered so as to be sensitive to the same wavelength range.

It can be seen from FIGS. 2a and 2b that the emitter/ray receiver pair20, 22 and light gate 18 therebetween is offset by a distance 24 to oneside of the centre of the glass 4, e.g. offset by 10 mm. Theemitter/receiver pair 20, 22 is positioned so that the light gate 18 isat the same height as the thickened base of the glass 4. Lenses 26 thatare clear to infrared light can be used to hide the emitter 20 andreceiver 22 and protect them from frost growth. For each sensor reading,a controller turns the LED emitter 20 on and off 50 times and converts adetection signal from the receiver 22 at each step by a 10-bit ADC toeliminate ambient infrared from the reading. The on and off values aresummed separately, and the off total is subtracted from the on total. Ithas been found that such an infrared sensor arrangement works best witha narrow beam LED with a half angle of 20° or less. For example, theemitter 20 may be an 8° half angle LED, for which typical sensor readingvalues are 3,000-4,000 without a glass present and 200-300 with a glasspresent, giving at least a 10:1 ratio, which allows a simple thresholdfor the detection signal to determine whether a glass 4 is present ornot.

Another non-contact sensor arrangement is seen in FIGS. 3 and 4. Thisarrangement uses passive thermal emission in the far infrared spectrumto detect an ambient temperature glass 4 that is inserted through anaperture defined by the flexible membrane 16. As seen in FIGS. 3a and 3b, a far-infrared (FIR) thermopile sensor 28 is positioned to point downat an angle through the opening to the cold heat transfer cavity insidethe device. The field of view 30 of the sensor 28 includes the less coldaperture seal 16 as well as the aperture itself. When a glass 4 isinserted (FIG. 3b ), much of the field of view 30 is filled by the baseof the glass 4, which is at ambient temperature. The thermal emissionimage shown in FIG. 4 shows that the ambient temperature glass 4 isclearly visible against the cold aperture and aperture seal 16. Whiletypical temperatures sensed for the aperture may be −15° to −35°, theambient temperature glass 4 gives about 40° C. swing in reading.

Another non-contact sensor arrangement is seen in FIGS. 5a and 5b . Inthis example the presence of a glass 4 in the heat transfer cavity 6 isdetected by measuring changes in capacitance. Glass in particularprovides for good detectability in air because it has a relativepermittivity of between around 4 and 10. In this capacitive sensorarrangement, electrodes 32, 34 are arranged in the heat transfer cavity6 on either side of the ducting member 8, so that an inner electrode 32is positioned inside the inserted glass 4 and an outer electrode 34 ispositioned outside the glass 4. To eliminate sensitivity to local icebuild-up and improve glass protection capability, concentric annular(e.g. cylindrical/frustoconical) electrodes 32, 34 are used to increasesurface area. Such an arrangement is less proximity-dependent so thatthe build-up of a thin ice or frost layer on the surfaces of the glass 4does not affect sensor readings. It has been found that good glassdetection sensitivity can be achieved with an electrode separation ofseveral centimetres, even with two layers of plastic ducting member 8 inseries. The electrodes 32, 34 may be provided as annular plates, or maytake the form of conductive coatings applied to the plastic ductingmember 8 or other suitable surfaces inside the housing of the device 2.Conductive paint (such as that used for EMC shielding), printedconductive tracks and chromed finishes are all appropriate methods ofachieving sufficiently effective electrodes 32, 34. If the ductingmember 8 carried the electrodes 32, 34 and it is removable, then aseparable electrical connection may be required. As is seen most clearlyfrom FIG. 5b , the ducting member 8 may be removably positioned over aninner moulding 36 that carries the capacitive sensing electrodes 32, 34.The inner moulding 36 may be permanently positioned inside the devicehousing. The inner moulding 36 includes an inner tube 38 that runs upthe inside of the ducting member 8 to prevent fingers from reaching thefan (not shown) when the ducting member 8 is removed. The inner tube 38is an ideal part to apply a coating for the inner electrode 32 so thatit penetrates deep inside the glass 4 without any need for an electricalconnection to the ducting member 8. The outer electrode 34 may be fittedinside the moulding 36, or alternatively a coating can be applied to aninner surface of the cylindrical moulding 36.

FIG. 6 provides a side sectional view similar to that seen in FIG. 1a ,except that details of the fan 12 are visible. It can be seen that theelectric fan 12 comprises a rotating arrangement of vanes or bladesmounted on a hub 40. The hub 40 is driven by a rotating drive shaft 42with bearings 44 arranged therebetween. The shaft 42 extends from a fanbase 46 that has an electrical connection to ground 48. An impedance 50may optionally be added to the grounding line so as to prevent any EMCemissions if electrical noise is present, by reducing the ability of thehub 40 to act as an antenna. It has been found that there may besufficient electrical conduction through the bearings 44 that connectthe fan base 46 to the hub 40, but other connection methods are alsopossible. Earthing of the fan hub 40 means that a metallic hub can beused instead of a plastic hub. It has been found that when ice crystalsare ingested into the fan 12 it can cause a malfunction. This is oftenonly momentary, but occasionally terminal for the fan motor and itscontrol board. The cause of this malfunction is believed to beelectrostatic charge separation seemingly caused by the high velocity(e.g. 30-50 mph) impact of ice crystals onto the fan hub 40, asgenerally indicated by the arrows in FIG. 6. It seems that sufficientcharge may build up on the hub 40 to cause an electrical arc to the fanmotor or drive electronics below, affecting operation of the fancontroller.

Any of the non-contact sensor arrangements described above may be used,alone or in combination, to detect when an object such as a glass isinserted into the heat transfer cavity of a cooling device. A controllerconnected to the fan may then adjust the rate of circulating airflow inresponse to a detection signal from the sensor arrangement. Insertion ofa glass or other object may trigger a rapid cooling mode in which thefan speed is increased. Readings from the sensor arrangement may also beused by the controller to decide when to switch the cooling devicebetween peak and off-peak modes of operation, for example when it isdetermined that the cooling device has not been used for a certainperiod of time.

In addition to the modes of operation mentioned above, the coolingdevice may be operated in a defrost mode where the heat exchanger 10 isturned off and the heat transfer cavity 6 is allowed to defrost. As inseen in the schematic of FIG. 7, the heat transfer cavity 6 may beprovided with an outlet valve 52 that enables fluid to leave the heattransfer cavity 6, for example to drain water produced during defrost.During a defrost mode of operation, the flow of refrigerant through theheat exchanger 10 may be stopped so that the coils begin to warm upunder the thermal load. The fan 12 may be turned on to full power so asto circulate the air as it warms up and assist in drying out the heattransfer cavity 6. When the defrost mode is activated, the outlet valve52 may be opened so that air is pulled through the heat exchange cavity6 and liquid can drain out. As indicated by arrow 54, ambient air may bedrawn in through the upper opening 14 and the circulating air movementhelps to exchange heat and moisture with the outside world through theventing flow 55 provided by the outlet valve 52. The high air speedcreated by the fan 12 can act to quickly clear droplets of water createdfrom condensation and melted frost. In addition, the increase in powerdissipated by the fan 12 can help to warm up the inside of the coolingdevice 2, helping to melt and evaporate frost and increasing thecapacity of the airflow to carry water vapour. The fan 12 may includepotted or coated electronics so as to be unaffected by moisture ingress.

The flow path to the outlet vent 52 and its position will now bedescribed in more detail with reference to FIGS. 8 and 9. As seen fromthe top view of FIG. 8, the heat transfer cavity includes an exit 56 tothe outlet valve 52 is at a point near the periphery of the fan 12. Theflow path indicated by the arrows 60 is arranged to run towards the exit56 tangential to the direction of rotation 58 of the fan 12. This pointin the air circuit is at relatively high pressure, whereas the opening14 is at relatively low pressure, and so ambient air is drawn in throughthe top of the heat transfer cavity 6 and ejected through the outletvent 52. The position of the exit 56, outside the fan 12 and angledtangentially, not only benefits the air pressure recovery—encouraginggood flow—but also allows spray that is flung tangentially from the fan12 to be collected effectively. Furthermore, the floor of the heattransfer cavity 6 around the fan 12 may slope downwards towards the exit56 in the general direction of air flow, allowing water collected in thebottom of the cavity 6 to drain out through the vent 52. The arrows 60in FIG. 8 indicate how the floor of the heat transfer cavity 6 slopescontinually downwards towards the exit 56. Furthermore, the arrows 62and 64 indicate how the floor of the heat transfer cavity 6 may beinclined in a radial direction, on both sides, so that liquid runs downonto the outlet flow path 60, which is then sloped downwardly in acircumferential direction towards the exit 56. In other words, the baseof the heat transfer cavity 6 may be designed to provide a helical flowpath that collects and drains liquid towards the exit 56.

The outlet valve 52 is seen in more detail in FIGS. 9a-9c . The outletvalve 52 comprises an outlet opening 66 leading out horizontally fromthe exit 56. A movable cover 68 is operated by a servo motor 70. Theopening 66 is positioned above a funnel 72 designed to catch droplets ofliquid as they drip out of the opening 66, which is provided with apointed protrusion 74 that encourages any droplets remaining attached tocollect directly into the funnel 72. The funnel 72 narrows to an exittube 76 which is designed not to restrict airflow out of the valve 52 byhaving internal dimensions of 12.5 mm by 9 mm (95.1 mm²). The tube 76passes through the bottom of the housing of the cooling device 2 so asto direct liquid into an external drip tray 78. As is seen in thecross-sectional view of FIG. 9b , the exit tube 76 has a pointed end 80to clear drips more effectively. Melt water collected in the drip tray78 can be left to evaporate or may be emptied out. The drip tray 78 maybe removable for this purpose. It has been found that the exit opening66 should ideally provide an unrestricted airflow path to promotecirculation and dry out the heat transfer cavity quickly. For acceptabledefrosting times, e.g. about 20 minutes (depending on ambientconditions), the exit 56 and flow path to the opening 66 may be madelarger than 50 mm² in cross-section along its length. The entire exitpath may be more than 300 mm² to provide for effective drying in arelatively short time period. The opening 66 may be a tube having aninternal diameter of about 18.5 mm. From the cross-sectional view ofFIG. 9c it can be seen how the opening 66 is at the end of a tube thatextends generally horizontally through the housing from a periphery ofthe fan 12. Furthermore, comparing the left and right sides in FIG. 9c ,it can be seen that the base 7 of the heat transfer cavity starts higheron the left side and then spirals downwardly, around the outside of thefan 12, to reach a low point at the exit 56 to the outlet opening 66.

The servo motor 7 operates to open the outlet valve 52 whenever thecooling device 2 enters a defrost mode. In addition, the device 2 may bedesigned to automatically enter a defrost mode in the event of a powercut. It is important that the glass froster i.e. cooling device 2 isable to drain if affected by a power cut, to avoid an unhygienic pool ofwater being trapped in the bottom of the device as it warms up. While itis not possible to operate the fan 12 to assist in defrosting withoutpower, sufficient energy can be stored to open the outlet vent 52 justas the power is cut off, at least enabling the unit to drain. Thecontroller may include an extra capacitance to store energy powering thelogic and servo motor 70, as well as means of detecting a drop in thesupply voltage. In an alternative system, the motor of the fan 12 may beturned into a generator by electric braking, thereby converting theremaining kinetic energy of the spinning fan into power to operate themotor 70 and open the vent 52. In some examples, the servo motor 70 maybe replaced by a solenoid actuator with the cover 68 being sprung openbut held closed by an electromagnet, such that when necessary, or whenthe power supply is cut, the electromagnet releases the spring and thecover 68 is opened.

FIG. 10 shows the cooling device 2 in the form of a countertop or bartop unit including an on-board controller 82 and a clamp 84 to mount theunit to a counter surface. An umbilical cord 86 is used to transferrefrigerant fluid and power to the cooling device 2. FIGS. 11a and 11billustrate how the umbilical cord 86 may be connected to a separaterefrigerant device 88 at 45 degrees, such that it can be bent either tolead vertically upwards or horizontally. A reversible cover plate 90 canthen be attached in one of two orientations, depending on the directionof umbilical cord 86 that is required to fit different countertoparrangements.

Finally, it is seen with reference to FIG. 12 how the umbilical cord 86may transfer coolant fluid e.g. refrigerant between the refrigerantdevice 88 and the bar top cooling device 2, as well as relaying controlsignals 92 and providing an electrical power supply 94. The coolerdevice 2 includes heat exchanger coils 10, fan 12, defrost valve 56,controller (e.g. PCB) 82, temperature sensor 96, glass detection sensor98, display 100 and control interface 102. The refrigerant device 88includes a mains power cable 104, a DC power supply 106 for the coolingdevice 2, a fridge control relay 108 and a condensing unit 110. Signalsfrom the controller 82 in the cooling device 2 may be transmitted to thefridge control relay 108 so as to determine when the apparatus isoperating in peak or off-peak mode. Any suitable coolant fluid may beused, for example a refrigerant such as R404A.

In peak mode, the condensing unit 110 may be constantly running and thesensor 96 used to monitor the temperature inside the cooling device 2 soas to maintain the heat transfer cavity in a desired temperature rangee.g. −35° C. to −45° C. In off-peak mode, the heat transfer cavity maybe maintained at a higher temperature by turning off the condensing unit110 for some of the time, e.g. maintaining the cooling device in thetemperature range of −25° C. to −35° C. Periodically turning off thecondensing unit 110 results in a lower average heat transfer rate in theoff-peak mode. The compressor in a typical condensing unit 110 cannot beturned back on for one minute (or more) after being turned off due tothe back pressure, meaning there could be a significant rise in internaltemperature of the cooling device 2. This would affect peak throughput,as the extra load of cooling glasses would worsen the rise while thecompressor needs to stay off. In the off-peak mode, however, by notneeding to frost a glass as quickly, such a temperature rise would beacceptable, so cycling the fridge compressor on and off is an effectiveway of lowering the power consumption significantly.

The higher internal temperature in the off-peak mode may be compensatedby an increase in the time spent frosting a glass, which would be lesssignificant to performance during off-peak times of use. The controllers82, 108 may respond to glass detection signals from the sensor 98 toprovide a faster cool down reaction to increased loads, e.g. frosting ofmultiple glasses in a series. This may be in addition to the controller82 increasing the speed of the fan 12 when the glass sensor 98 providesa detection signal that causes the cooling device 2 to switch into rapidcooling mode. The system may include a time delay before switching intooff-peak mode, to avoid cycling the condensing unit 110 (especially thecompressor) too often, to prevent damage or excessive wear. If thecondensing unit 110 was turned off more than e.g. two minutes ago, theninserting a glass may make it turn back on automatically. Whenresponding to an inserted glass in off-peak mode, the rate at which theinternal thermal mass warms will increase under the load of frosting aglass, but there will be a delay before this is detected by temperaturemeasurement. Therefore turning on the condensing unit 110 when the glassis inserted can improve performance.

The fridge condensing unit 110 in the refrigerant device 88 may include,as is conventional, a compressor to pressurise the coolant fluid e.g.refrigerant returning from the cooling device 2, a condenser to removeheat from the fluid, and an expansion device to rapidly cool the fluidbefore it is supplied back to the cooling device 2. However, there isenvisaged an embodiment in which the expansion valve is instead providedwithin the cooling device 2, so that warmer refrigerant is transferredfrom the refrigerant device 88 to the cooling device 2 via the umbilicalcord 86. The umbilical cord 86 may then allow for energy regeneration,hot refrigerant flowing out transferring heat to the cold refrigerantreturning. Additionally, the higher average temperature in the umbilicalcord 86 may mean reduced heat gain through its insulation or even areduced thickness of insulation required. The umbilical cord 86 may be aflexible tube containing cables to transfer power and control, and hosesto transfer refrigerant fluid between the refrigerant device 88 and thebar top glass froster 2. The umbilical cord 86 may have a quickdisconnect on the hoses, as well as a separable electrical connector.This may make installation considerably easier, as the two parts of thesystem can be installed separately. To ensure correct connection, theseconnectors may be designed poka-yoke by having one female and one maleconnector on the umbilical and one of each to match on the refrigerantdevice 88, such that they cannot be connected the wrong way round.

1. A heat transfer device comprising: a heat exchanger driven bymovement of a fluid therein, a heat transfer cavity and a fan forcreating a circulating gas flow between the heat exchanger and the heattransfer cavity; a housing having an opening for allowing an object tobe inserted into the heat transfer cavity; an outlet valve forexhausting gas and/or liquid from the heat transfer cavity; and acontroller arranged to operate the outlet valve.
 2. A heat transferdevice according to claim 1, wherein the heat transfer cavity comprisesan outlet flow path arranged to direct liquid towards the outlet valve.3. A heat transfer device comprising: a heat exchanger, a heat transfercavity and means for creating a circulating gas flow between the heatexchanger and the heat transfer cavity; a housing having an opening forallowing an object to be inserted into the heat transfer cavity; and anoutlet valve for exhausting gas and/or liquid from the heat transfercavity; wherein the heat transfer cavity comprises an outlet flow patharranged to direct liquid towards the outlet valve.
 4. A heat transferdevice according to claim 2, wherein the outlet flow path is inclineddownwardly in a radial and/or circumferential direction so as to directliquid towards the outlet valve.
 5. A heat transfer device according toclaim 2, wherein the outlet flow path provides a helical incline towardsthe outlet valve.
 6. A heat transfer device according to claim 1,wherein the outlet valve comprises an outlet opening that is directedsubstantially tangential to the direction of the circulating gas flow.7. A heat transfer device according to claim 6, wherein the outletopening is substantially positioned at a periphery of the fan.
 8. A heattransfer device according to claim 1, wherein the outlet valve comprisesan outlet opening having a cross-sectional area of at least about 50mm².
 9. A heat transfer device according to claim 1, further comprisinga funnel arranged adjacent to the outlet valve to collect liquid.
 10. Aheat transfer device according to claim 1, wherein the heat transferdevice is a cooling device and the heat exchanger is a thermal sinkarranged to cool the circulating gas flow.
 11. A heat transfer deviceaccording to claim 1, wherein the controller is further arranged tocontrol the fan.
 12. A heat transfer device according to claim 1,wherein in a (“defrost”) mode of operation the heat exchanger is nolonger driven and the controller opens the outlet valve.
 13. A heattransfer device according to claim 12, wherein in the (“defrost”) modeof operation the controller operates the fan at an increased speed so asto circulate the gas flow more rapidly.
 14. A heat transfer deviceaccording to claim 12, further comprising a heater operating in the(“defrost”) mode of operation, and optionally wherein the heat exchangeracts as the heater.
 15. (canceled)
 16. A heat transfer device accordingto claim 1, wherein the outlet valve is arranged to automatically drainliquid from the heat transfer cavity upon loss of electrical power tothe heat exchanger, or the controller operates to open the outlet valvein response to a power cut detection signal.
 17. (canceled)
 18. A heattransfer device according to claim 1, wherein the outlet valve is biasedopen but held closed by an electromechanical actuator.
 19. A heattransfer device according to claim 1, wherein the outlet valve isactively opened upon loss of electrical power.
 20. (canceled)
 21. A heattransfer device according to claim 1, comprising means for storingelectrical power and/or means for generating electrical power so thatthe outlet valve can be opened in response to a power cut. 22.(canceled)
 23. (canceled)
 24. (canceled)
 25. (canceled)
 26. (canceled)27. (canceled)
 28. (canceled)
 29. (canceled)
 30. (canceled) 31.(canceled)
 32. (canceled)
 33. (canceled)
 34. (canceled)
 35. (canceled)36. (canceled)
 37. (canceled)
 38. (canceled)
 39. (canceled) 40.(canceled)
 41. (canceled)
 42. (canceled)
 43. (canceled)
 44. (canceled)45. (canceled)
 46. (canceled)
 49. (canceled)
 48. (canceled) 49.(canceled)
 50. (canceled)
 51. (canceled)
 52. (canceled)
 53. (canceled)54. (canceled)
 55. (canceled)
 56. (canceled)
 57. (canceled) 58.(canceled)
 59. (canceled)
 60. (canceled)
 61. (canceled)
 62. (canceled)63. (canceled)
 64. (canceled)
 65. (canceled)
 66. (canceled) 67.(canceled)
 68. A method of drying a heat transfer device comprising aheat transfer cavity that can receive an object, the method comprising:creating a circulating gas flow in the heat transfer cavity; ceasing tocool or heat the circulating gas flow; and opening an outlet valve toexhaust gas and/or liquid from the heat transfer cavity.
 69. A methodaccording to claim 68, further comprising: increasing the rate of thecirculating gas flow.
 70. (canceled)
 71. (canceled)